hochverfügbarkeit mit mariadb enterprise - mariadb roadshow summer 2014 hamburg berlin frankfurt

Hochverfügbarkeit mit MariaDB Enterprise

MariaDB Roadshow 2014 Hamburg -‐ Berlin -‐ Frankfurt

Ralf Gebhardt, Sales Engineer [email protected]

© SkySQL – The MariaDB Company

Agenda

• IntroducSon to High Availability • Different services that need HA • Different components of High Availability • Different MariaDB HA SoluSons

•  HA using MariaDB ReplicaSon •  HA using MariaDB Galera Cluster


IntroducSon to High Availability

High availability is a system design protocol and associated

implementation that ensures a certain degree of operational continuity during

a given measurement period



• High Availability isn’t always the same as Long Up(me

•  A system that is “up” might sSll not be accessible •  A system that is “down” just once, but for a long Sme, isn’t highly available

• High Availability rather means •  Long Mean Time Between Failures (MTBF) •  Short Mean Time To Recover (MTTR)



• The level of availability is measured as the raSo of Sme the system is available over a year, expressed as a percentage

•  99.9% availability means that the system is available at least 8.751 of 8.760 hours in a year, or that it is unavailable at the most 9 hours per year •  99.999% availability means that the system is available at least 525.595 or 525.600 minutes in a year, or that it is unavailable at the most 5 minutes per year


Maintaining High Availability

• There are two common situaSons that we try to protect ourselves from using an HA soluSon

•  Datacenter failure – A whole datacenter becomes unavailable for some reason, like power failure, network failure, a virus or similar situaSons •  Server failure – An individual server fails because of a hardware failure or something similar


Services in an HA SoluSon

• All services that make up the applicaSon stack needs HA for the system to achieve HA

•  Web servers •  ApplicaSon servers •  ApplicaSons •  Database servers •  Storage •  Network

TCO for Unbreakable

Hardware


Services in an HA SoluSon

• Of the different types of services, there are two types

•  Stateless services These servers has no state beyond the current operaSon. If such a server fails, another server of the same type can replace it without having to transfer any set of data. Webservers and applicaSon servers are typical stateless services

•  Stateful services These services maintains a state, and that state needs to be preserved if a server fails, and has to be made available to any other server that takes it place. A database service such as a MariaDB server is a typical stateful service


Components of High Availability

• Monitoring and Management •  Availability of the services needs to be monitored, to be able to take acSon when there is a failure. A failover can be manual or automaSc, but it has to be managed

• Failover / Load Balancing mechanism •  Some mechanism to redirect traffic from the failed server or Datacenter and to a working one

• Data redundancy •  For stateful services, we need to make sure that data is somehow made redundant


Monitoring and Management

• There are many different soluSons here, some focused on specific services (in parScular database), some as part of a Load Balancing sogware soluSon of an Appliance or a pure sogware based soluSon such as LinuxHA, HAProxy, MaxScale, MHA


Failover mechanism

• There is a wide range of opSons here too, in parScular when it comes to Datacenter failover, which can be more complicated

• Common mechanisms range from applicaSon based failover and DNS failover to Load Balancing and Network Failover


Data Redundancy

• Providing Data Redundancy is complex, error prone and takes a toll on performance

• It also has to be menSoned that a SAN does not provide redundancy just because a disk set can be failed over from one server to another. A SAN might be a SPOF, but in some cases that is a risk that some customers is willing to take


Data Redundancy with MariaDB

• MariaDB Internal ReplicaSon •  Asynchronous •  Semi-‐Synchronous

• Storage based redundancy (AcSve/Passive) •  DRBD (Distributed Replicated Block Device) •  SAN (Storage Area Network) •  VMWare replicaSon

• MariaDB Galera Cluster


HA using MariaDB ReplicaSon

• This is in many cases a good enough soluSon, but it has some issues

•  The cluster is very loosely coupled, not all nodes are aware of all the other nodes for example •  ReplicaSon is asynchronous, so failing over is more difficult than usually (but MHA solves this) •  Adding a slave is difficult

• But there are also many advantages •  Low performance penalty •  Well known and easy to use technology


HA using MariaDB Galera Cluster

• This a sogware-‐only soluSon with many advantages

•  Scales writes and well as reads •  “Proper” Cluster with built-‐in failover, locking and split-‐brain protecSon •  Synchronous replica(on with low overhead due to opSmisSc locking

• There are some disadvantages •  More overhead than using Asynchronous ReplicaSon •  Only works with InnoDB •  For distributed writes, some restricSons apply


MariaDB Galera Cluster setup

MariaDB Server MariaDB Server MariaDB Server

Galera wsrep Library Galera wsrep Library Galera wsrep Library

Synchronous Replication

Load Balancer / Failover

Application / Application server


Sejng up MariaDB Galera Cluster

• MariaDB Galera Cluster consists of the MariaDB binary that in turns talks to the Galera wsrep library

• Once set up, Galera is configured using the usual my.cnf file, and is monitored using the SHOW GLOBAL STATUS command


MariaDB Galera Cluster failover

• MariaDB Galera Cluster handles failed servers internally

• MariaDB Galera Cluster also handles split-‐brain protec(on and this requires at least 3 servers

• MariaDB Galera Cluster can also be configured without split-‐brain protecSon, for example when failover is manual or is handled in some other way


MariaDB Galera Cluster setup

• If necessary to allow for protecSon against split-‐brain scenarios, but only using 2 database servers, a third server can be set up with a Galera specific arbitra(on agent

• Galera also can be used with it’s own simple Load Balancer, although it is much more common that other technologies are used, such as HA aware Connectors or a Load Balancer

Fragen?

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Vielen Dank!

Hochverfügbarkeit mit MariaDB Enterprise

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